The National Action Plan for Adverse Drug Event (ADE) Prevention identified three high-priority drug classes as key targets for reducing the risk of drug-related injuries: anticoagulants; diabetes agents (insulin and oral agents); and opioids. These medication classes were chosen because they account for the greatest number of measurable drug-related harms to patients, and a substantial proportion of ADEs associated with these medications is considered preventable. The overarching objective of the proposed project is to pursue a large clinical trial focused on older patients recently discharged from the hospital who have been prescribed anticoagulants, diabetes agents, or opioids. The clinical trial will determine the value of a multifaceted medication error and ADE reduction intervention with a special focus on in-home assessment. Components of the intervention will include: (1) in-home assessment of high-risk patients by a clinical pharmacist; (2) best- practice, evidence-based medication safety tools and resources targeted to high-risk patients and their caregivers; (3) communication with the primary care team via the electronic health record regarding concerns relevant to the use of high-risk medications as well as other medication safety concerns; and (4) a follow-up phone call by the pharmacist to the patient and/or caregiver within 14 days of the home visit. The primary outcome of interest will be clinically important medication errors, a composite outcome comprised of preventable or ameliorable ADEs and potential ADEs due to medication discrepancies or non-adherence. Secondary outcomes will include: (1) preventable or ameliorable ADEs; (2) potential ADEs due to discrepancies or non-adherence; and (3) preventable or ameliorable ADEs judged to be serious, life- threatening, or fatal. The knowledge to be gained from this trial is substantial. As stated in PA-14-002 (Advancing Patient Safety Implementation through Safe Medication Use Research), Reduction of adverse drug events (ADEs) is a top priority for the Department of Health and Human Services (DHHS), and a comprehensive strategy is in development in order to significantly reduce ADEs within the three classes which account for a significant proportion of all ADEs: anticoagulants, diabetes agents, and opioids. This research proposal aligns with this DHHS priority and with the Patient Safety Portfolio at AHRQ which is committed to the development, implementation and adoption, and wide-spread dissemination of tools and resources to improve health outcomes. The ultimate goal of the proposed research is to mitigate the public health burden related to ADEs among high-risk elderly patients (an AHRQ priority population) by demonstrating an effective intervention strategy to reduce this risk.